Go to http://mlm.home.cern.ch/mlm/alpgen/ and download
v213.tgzby clicking NEW: The source code for version V.213
untar/zip the file by typing
> tar -xzvf v213.tgz
2Qlib alplib hjetlib phjetwork topwork wjetlib wqqlib 2Qphlib compare hjetwork prc.list validation wjetwork wqqwork 2Qphwork compile.mk Makefile pylib vbjetlib wphjetlib zjetlib 2Qwork DOCS Njetlib QQhlib vbjetwork wphjetwork zjetwork 4Qlib ft90V.tar.gz Njetwork QQhwork wcjetlib wphqqlib zqqlib 4Qwork herlib phjetlib toplib wcjetwork wphqqwork zqqwork
cd wjetwork
alpgen.inc input Makefile pdflnk wjet.inc wjetusr.f
>make gen
wjetgen
1 ! imode w2j ! label for files 0 ! start with: 0=new grid, 1=previous warmup grid, 2=previous generation grid 10000 2 ! Nevents/iteration, N(warm-up iterations) 100000 ! Nevents generated after warm-up *** The above 5 lines provide mandatory inputs for all processes *** (Comment lines are introduced by the three asteriscs) *** The lines below modify existing defaults for the hard process under study *** For a complete list of accessible parameters and their values, *** input 'print 1' (to display on the screen) or 'print 2' to write to file njets 2 ptjmin 20 drjmin 0.7via
./wjetgen < inputand it will generate weighted events for W+2j for proton-antiproton collisions and for 980 GeV per beam [not what we want]. It will also produce the following additional files [run and look]:
cnfg.dat w2j.grid1 w2j.grid2 w2j.mon w2j.par w2j.stat w2j.top w2j.wgt
ih2 1 ebeam 7000to change the parameters to proton-proton collisions at 7000 GeV per beam. This is usually automatic in the CMS-ALPGEN version (v205 of production) but not in the version picked up from the MLM ALPGEN site.
1 ! generation tt3j ! string labeling the output files 0 ! start with: 0=new grid, 1=previous warmup grid, 2=previous generation grid5 1000000 4 ! N(events)/iteration and N(iter's) for initial grid optimize 10000000 ! number evts to generate *** The above 5 lines provide mandatory inputs for all processes *** (Comment lines are introduced by the three asterisks) *** The lines below modify existing defaults for the hard process under study *** For a complete list of accessible parameters and their values, *** input 'print 1' (to display on the screen) or 'print 2' to write to file ih2 1 ebeam 7000 mt 175.00 ihvy 6 njets 2 ptjmin 20 iqopt 1 ickkw 1 drjmin 0.7 etjmax 5 itdec 1 itdecmod 6
1000000 4 ! N(events)/iteration and N(iter's) for initial grid optimize 10000000 ! number evts to generateHere for the tt+3 jets I have asked 4 iterations of 1M events (this will create the grid1, warmup grid) and actual generation of 10M events. The final phase space grid I get is the .grid2. This is important for CRAB-ALPGEN production and this is what constitutes the first part of the "homework" per process per jet multiplicity and for the different cuts. ALPGEN improves its grid sampling iteration by iteration, so it is a good idea to use a few iterations, eventually with a reduced number per iteration. But there should be sufficient warm ups such that they are enough to sample a large fraction of the phase space. Otherwise, the grid would be unstable for a lot of iterations and not really improving. As a rule of thumb, since the 05 production I have used a few millions per iteration and chosen the number of iterations to be N+1 or N+2 where N is the number of partons.